High speed telegraphy



July 18, 1933. R. DUNHAM 1,918,252

HIGH SPEED TELEGRAPHY Filed' May 25, 1931 5 Sheets-Sheet 1 1. +2.50 -/00FIG.

INVENTOR C. R. DUNHAM ATTORNEY July 18, 1933. Q R DUNHAM 1,918,252

HIGH SPEED TELEGRAPH! Filed May 25, 1931 5 Sheets-Sheet 2 lnnnnnfinnhmnnnnnnl-L HFLTLFIFLFIHHH INVENTOR C. R. QUNHAM ATTORNEY July 18, 1933.c. R. DIUNHAM I 8, 5 I HIGH SPEED TELEGRAPHY Filed May 25, 1931 5Sheets- Sheet 3 INVE N 70/? C. R. DUNHAM 91% I A5 IL J l I II I'D W FIG5 July 18, 1933.

c. R. DUNHAM HIGH SPEED TELEGRAFHY Filed May 25, 1931 5 Sheets-Sheet 4 ATTORNEV July 18. 1933. V Q DUNHAM 1,918,252

HIGH SPEED TELEGRAPHY Filed Ma 25. 1951 5 Sheets-Sheet 5 1.4 m m i 2.83.0 .1 LJ L. 4.x/ U I U l4. x/ys L| i U /5.X/V6 TL L INVENTO/P C. R.DUNHAM.

A T ORAZEY Patented July 18, 1933 written stares teiazse rarest oIf-FicaCARLTON ROSSLYIN DUNHAM, OF ALDW SZCH, LONDON, ENGLAND, ASSIGNOE T0WESTERN ELECTRIC COMPANY, INCORPORATED, 015 NEW YORK, Y lA. CORPORA-TION OF NEW YORK HIGH srnnn rnLnGitArHY Application filed may 25, 1931,Serial No. 589,687, and in' Great Britain June 12, 1830.

This invention relates to electric circuits and provides an arrangementof energy translators such as three electron discharge devices which mayhave a variety of uses, but is particularly applicable for use as adistributor for high speed telegraphy.

One object of the invention is to provide a high speed telegraphdistributor having no mechanical or moving parts.

Another object of the invention is to cause a series of current impulsesof one frequency to produce another series of impulses of the same ordiiferent frequency with a definite control of the time relation atwhich the impulses occur.

According to a feature of the invention, a group of electrical energytranslators is adapted to control the operation of an associated groupthroughout an assembly of such groups. An arrangement of this kind maycomprise a plurality of valve circuits each of which is connected to theone following it in such a way that an impulse applied to any one of thevalve circuits makes it operative for a short interval of time and animpulse is then passed on to the next valve circuit which is therebymade operative for an equal interval and so on through the remainder ofthe circuits in succession. A wave (preferably square) may be appliedfrom an external origin to control the length of the interval duringwhich each circuit is operative and hence the speed at which theoperating condition passes down the line. This speed is thereforecontrollable and by coupling together the last and first row of valvecircuits the system maybe made cyclic in operation.

According to another feature of the invention the arrangement is suchthat a particular valve or valves in an assembly can operate as anamplifier only when all the valves of a certain set of one or more othervalves are paralyzed.

According to another feature of the invention, a distributor which givesimpulses for the purpose of operating external apparatus is so arrangedthat the impulses are given by units preceding the one for which theresults of the operation of the external apparatus are intended, so thatthe time talfen in the operation of the external apparatus may beaccounted for.

According to another feature of the invention an arrangement comprises aplurality of groups of valves, one valve in each group being subjectedto an impressed pulse adapted to change its condition as from beingoperative or non-operative, and means are associated with the saidvalve, which due to said change, produce an opposite change in anothervalve of the same group which for a predetermined time maintains thechan ed condition of the first said valve. Other eatures of theinvention will be disclosed in the following description havingreference to the accompanying drawings, in which:

Fig. l is a schematic representation of an arrangement according to thepresent invention;

Fig. 2 gives a plurality of curves representing certain conditions inthe circuit of Fig. l. and is used to explain a principle of the in--vention;

Fig. 3 schematically shows the invention in the form of a receivingdistributor for telegraphy or the like;

Fig. 4 illustrates a modification which may he made in the distributorof Fig. 1;

Fig. 5 illustrates a frequency divider according to the presentinvention and Fig. 6 is a set of curves used to describe the operationof the arrangement of Fig: 5.

The arrangement of Fig. 1 shows a plurality of groups or units eachconsisting of two valves such 'as V11 and V12 These units with theirassociated circuits are similar and therefore the description of oneunit with 1ts associated circuits will serve to ex lain the paralyzedand will pass no plate current.

The resistances R211, R212, and R213 form. a potentiometer connectedacross points of a and the 3rd, 6th, 9th, 12t

battery F and H, which are at potential 250 volts and 100 volts withrespect to the com mon filament potential of all valves. Plate currentis supplied from the point F to the valve V21 via the resistance R211-The values of the resistances R211, R212 and R213 are chosen such that,when the grid voltage of V21 is 6 volts or more nega- Y tive, thepotential at the junction X2 of R212 and R213 is 2 volts, andthat whenthe grid voltage of V21 is -2 volts, the potential at the junction X2 ofR212 and R213 is 10 volts. This change in voltage is obtained by virtueof the potential drop owing to the passage of the plate current throughR211. In an exactly similar fashion there is associated with V22 apotentiometer of three re sistances R221, R222 and R223. Grid leaks L211and L212 of equal value connect the rid of V21 to thejunction Y2 ofresistances 222 and R223, and also to the point B, to WhlCh there isapplied a square wave which has a voltage with respect to the filamentvoltage of 2 volts for half its cycle and of 10 volts for half itscycle. Thus the rid voltage of the valve V21 is the mean 0 thepotentials at B and Y2, and therefore the valve V21 can operate onl (asan amplifier) when the potentials at B and at Y2 are both 2 volts. IThat is the valve V21 can operate only when the square wave B is in theless negative half of its cycle and when the valve V22 is inoperative.It is to be noted in particular that if the valve V22 1s operated, thevalve V21 cannot become operative in any part of the cycle of thecontrolling wave.

The grid voltage of the valve V22 is the mean of the potentials at X2and of X1 which is the corresponding point of the previous unit. Hencevalve V22 is operative only when both V11 and V21 are inoperative. Inthe remaining valve units the controlling waves for the 1st, 4th, 7th,10th group, are taken from points A, for the 2nd, 5th, 8th, 11th group,from point B, from point C. The waves A, B and C are similar in form butB is retarded by 120 with regard to A, and C by 120 with re aid to B.The other groups are composed 0 similar parts to these escribed and inorder to show this in the drawings the reference letters which usedthroughout each group contain one numeral identifying the roup, this.group identification being given y the first numeral appearing r thereference letter. v Considering the operation of the system as a whole.it is seen that if the point X0 is given a potential 2 volts, a. stablecondition is attained when the left hand valve in each unit or group isinoperative, and the right hand valve operative; the points X1, X2, X3have potential 2 volts, the points Y1, Y2, Y3 10 volts. This a workingimpulse to thevalve V22 in the next unit. This action continues untilthe square wave applied to B gets in its less negative half cycle, whenthe valve V21 becomes operative. At a subsequent instant, the squarewave applied to A falls to its negative half cycle, the valve V11becomes inoperative,.the valve V12 operative (I have assumed that theimpulse applied to X0 has by this time been removed). Thus the unitcomprising V11 and V12 is restored to normal condition and it remainsso, until a further impulse is applied to X0. The imulse that this unithas applied to the valve V22 makes the second unit operative during thelessnegative half of the cycle of the wave B, passing a further impulseto the valve V32 in the third unit.

The train of operations continues, all the valve units in the systembecome operative in turn until the last unit is reached. If the point Xnin the last unit is joined to the point X0 a cyclic arrangement of unitsis produced (there being a multiple of three units), and the train ofoperations continues round the circle endlessly.

The manner in which the apparatus described above may be used as thetransmit ting distributor of a telegraph system will now be described.K1, K2, K3 indicate contacts of the several transmitters that aredesired to be connected to the line L in turn. Consider the circuitthrough the contact'Kl. During that part of the cycle in which the valveV11 is operative, high frequency current passes (or fails to pass,according to the position of the contact K1) from a source P, via thesmall condenser C11, valve V11, small condenser C12 to the valve Va andthence to the line L. Similarly when the second unit is in operation,high frequencycurrent passes or does not-pass by the contact K2, via thevalve Vb to the line. The valve Va is interposed in the 1st, 4th, 7th,group circuits, Vb in the 2nd, 5th, 8th, group circuits, V0 in the 3rd,6th, 9th, the function of these valves being to correct the length ofthe signal impulses applied to the line. This is necessary owing to thefact that impulses supplied from the distributor proper would otherwiseoverlap each other, and is accomplished by applying to the grids of thevalves Va, V0 and V0, three square waves a, b and a (see Fig. 2),

each of which has the positive portion of its cycle half as long as thenegative. Thus the valves Va, Vb and V0 are each paralyzed throughtwo-thirds of each cycle, and function through one-third of each cyclein turn as normal amplifiers passing the signals to the line so thatthey do not overlap. Fig. 2 shows the respective configurations of thesix waves A, B, C, a, b, and c. It will be seen thatall these waves havethe same fundamental frequencies and can therefore be derived from thesame oscillator.

In order to correlate the mechanical operations of the severaltransmitters with the electrical operations of the distributor, a leadfrom any one point X0, X1 or Y1, Y2 (or if necessary more than one) inthe system may be taken and a positive or negative impulse once percomplete cycle of the distributor may be obtained therefrom. Thisimpulse may be used to work a relay train or perform any other desiredfunction. It is clear that the time taken in the operation of the relaysmay be compensated for by using an impulse derived from a point X or Ymore advanced in the cycle of the distributor than that instant at whichthe effect resulting from the operation of any particular relay isrequired. To operate an amplifier or vacuum tube device of a known kindwhich assumes and retains a certain condition when affected by animpulse until restored by a second impulse (usually of opposite sign) itis clear that a second impulse may be applied to it at a subsequentpoint of the cycle in order to restore the amplifier or device to itsnon-operated 'or original condition.

Fig. 3 is a symbolic diagram showing the arrangement at a receivingterminal. The high frequency current signaling impulses which arereceivedover the line L may be considered as a succession of separatehigh frequency impulses;theyareseparated fromeach other by the threevalves Va, Vb, V0 (which are made operative in turn by the three squarewaves a, b and c) and pass alternately to the leads P, Q, and R. Thedistributor D (which is exactly similar to the transmitting distributor)controlled by the square waves A, B and C distributes these impulsesconsecutively to the row of amplifiers A1, A2 which in turn control theoperation of the several printers PR. Leads B1, B2 are shown connectedto these amplifiers. These leads are connected to subsequent sections ofthe distributor and serve to restore the amplifiers iif they have beenoperated by the arrival of a high frequency impulse) in readiness fonthenext cycle of the distributor. The mechanical operation of the severalprinters may also be controlled by impulses taken from the distributor.

In Fig. 2 t shows a possible configuration of the envelope of the highfrequency impulses delivered by thetransmitter, whereas 1- shows Whatmight be expected at the B and C are the square waves controlling thedistributor. If the positive portions-of the cycles of waves a, b and care made equal to half the negative portions, the whole of each impulseas received will be applied to the distributor. The impulses whenreceived may be badly distorted; this distortion may lead to falseoperation of the printers. If the positive portions of the waves a, band c are made very short, only the central portions of each impulsewill be applied to the distributor. These. portions are shown shaded inr, and it is clear that they will lead to a truer operation. of theprinters than otherwise. It is clear that in a system consisting of atransmitting distributor and a receiving distributon'exact synchronismcan be maintained if the controlling waves at both ends have the samefrequency. This can be attained if the waves come fundamentally from thesame source. For instance, an oscillator at the transmitting end maysupply the waves required there, and the frequency transmitted over theline may be amplified to supply the waves required at the receiving end.Alternatively an oscillator may supply the waves required at thetransmitting end; at the receiving end the waves required may be derivedfrom a source whose frequency is controlled by the frequency of thetelegraph impulses supplied over the line. In the above case, thefrequency required for the controlling waves is two-thirds the dotfrequency of the system.

The progressive distributor of Fig. 1 can be simplified by thearrangement as shown in Fig. 4 which shows the schematic diagram for afive-unit channel of such a distributor. The same scheme of referencedesignation is used hereas in Fig. 1. Comparing this circuit to the oneof Fig. 1 it I is seen that fewer resistances are required. The plate ofvalve V21 is connected to the lower terminal of the leak resistanceL222. The plate is also connected over the resistance R21 to the hightension positive HT and over a condenser C22 to a terminal T21. The gridof the tube V21 is connected over a condenser 021 to a terminal T22. Thecarrier circuit is from terminal T12 to terminal T22. The plate of thevalve V22 is connected over a resistance L211, to the grid of valve V21.The saidplate of the valve V22 'is also connected over a resistance. R22to the high tension positive.

The grid of the valveV21 is connected through a resistance L212 to-aterminal T23 which is connected to a source of square waves B. Theterminal T24 is connected over a resistance L221 to the grid of thevalve V22 and the impulse for initiating the operation of thedistributor unit is impressed at T24 from the plate of the valve V 11 inthe previous unit. The arrangements connected to valve V11 and valve V31are similar to those connected to valve V21 except that the square waveis from A and C respectively and is displaced in phase as in the case ofFig. 1. A permanent grid bias for the tubes V12, V22,.etc., is obtainedthrough resistances L123, L223, etc., from grid bias battery GB.

A unit or group (e. g. that comprising valves V21 and V22 whosecharacteristics I will assume to be as described in connection withFig. 1) has grid leaks L212, L211, L222, L221 and L223 (each 0.5megoluns) and grid biasing battery GB which may be of, say -2lil) voltsif the plate voltagell. T. be 130 volts, the low tension positiveterminal L. T. being considered to be at zero potential. Resistances R21and R22 are 60000 ohms.

In the arrangement shown, if valve V21 be inoperative, the voltage atthe point T34 of L222 will be +130 volts with respect to the groundedfilament, if V11 be inoperative, the voltage at T21 will be +130 voltswith respect to the grounded filament and therefore the bias on the gridof valve V22 will be zero with respect to the plate of V22; and henceV22 is operative. If V11 becomes operative the potential at T24 falls to7 0 volts because of the drop of potential in R11 and the valve V22 ismade inoperative by the bias of 20 volts on its grid. This value of 20volts fol'iows from the facts that GB is at 260 volts, H. T. at +130volts, and from the potential drops in the resistances L221. L222 and1.223 with respect to the filament of V22. The voltage drop across R22therefore ceases and the upper terminal of L211 has its potential raisedto 130 volts,

i. e. that of H. T. This raising of the voltage at the terminal of L211makes the grid of the valve V21 have a bias of zero so that V21 isinoperative if the square wave B isv in its less negative half cycle(when its potential is -13O volts), and being operative there is apotential drop across R21 which reduces the potential of the lowerterminal of L222, thereby maintaining the bias of 20 on the grid ofvalve V22 even after the cessation of the pulse impressed on T24 whichcaused" the original change in the circuit. If the square. wave B be inits more negative half cycle (potential 170 volts), V21 does notoperate. The operation of the distributor units in sequence is thereforeas described with reference to Fig; 1.

In Fig. 5 is shown how the circuit arrangement accordingto the presentinvention may be used for frequency division. The points X1, X2, etc.and Y1, Y2, etc. correspond with the similar identified points'in Fig. 1and the squarewaves as in Fig. 1 are impressed at A, B and C. In thefigure X1 is shown connected over a condenser to a terminal I1 and Y3over another condenser to I2, of a flipflop device P. This device hastwo stable conditions, one producing one potential at the terminal 0,and the other a diflerent potential at that terminal. In the figure,when X1 gives its negative impulse, the valve T2 becomes operative whilewhen the point Y3 gives its negative impulse the valve T becomesoperative: With either T or T2 operative and the other valvenon-operative the device P is in a stable condition. Thus the output 0of the flip-flop device P gives a square wave of frequency equal to thefrequency of the cycle of the distributor, which may be for example halfthe frequency of the controlling square wave.

Fig. 6 shows, in 1, 2 and 3, the three phases of the controlling waves,in 4, 5 and 6 impulses given by X1, X2 and X3, in 7, 8 and 9 impulsesgiven by Y1, Y2 and Y3. 10 shows the output of the flip-flop when itsgrids are connected to X1 and Y1, 11 shows the output when connected toX1 and Y2, and so on. It is clear that-square waves of a variety ofphases and ratios of crest to trough can be obtained by choosingsuitable X and Y points to connect to the flip-flop device.

If a distributor of groups or 9 units (for a 3-phase controlling wave)is used, division of frequency by three may be obtained. If one ofthegrids of the flip-flop device be connected (by high resistances andcondensers) to two different X points, and the other grid to two Ypoints, the output of the fliptlop device will have two crests and twotroughs per cycle of the distributor. It will not in this case bepossible to make the crests appear at equal intervals, so that strictlyspeaking the output frequency cannot be said to be twice the frequencyof the distributor cycle and two-thirds that of the controlling Waves.However, if a 4-phased controlling wave be used employing a distributorof 12 units, it will be possible to make the output wave. double thefrequency of the distril ntor cycle, and therefore two-thirds thefrequency of the controlling waves. By similar means it is possible toprovide frequency dividers for square waves giving all simple ratiossuch as A,, etc.; in order to obtaina division by 2, four square waveswould be employed with eight valve units and the points X1 and Y3 wouldbe connected to the flip-flop device. Generalizing, the frequency of thechanges or kicks in the device the number of square waves.

- It is clear that one distributor may be used to worktwo or moreflip-flop devices at the same time so that a plurality of square wavesof various shapes, phases and frequency may be obtained from one and thesame distributor. The distributor may at the same time be used foranother purpose, such as for instance a telegraph transmitting orreceiving distributor.

The device substantially as shown in Fig. 1 or 5 may also be used as atiming circuit, and this in the following manner:

Suppose there are a number of units of a distributor connected togetheras usual, but without the last connected to the first so that they arein a row instead of in a cycle. Under the influence of the controllingwaves, this row will remain in a normal state with all selecting valvesparalyzed, but if an impulse be applied, it will be transmitted down therow at a definite rate and will emerge at the last unit after a fixedtime where it may be made to serve some useful purpose either directlyor by the aid of 'a flip-flop device. Thus the arrangement is a timingcircuit, which will act at a definite interval after any given action.Moreover its delay is adjustable and exact. Such a system could be madeto give a series of impulses in sequence after regular or irregularintervals. system it might be convenient to divide the distributor intociasses of units, some of which were controlled by square waves of onefrequency and'some by square waves of another frequency.

Although the description has been restrict ed to specific circuitarrangements, the principles involved in the invention are capable ofapplication in a. variety of specific forms to perform a variety offunctions.

.What is claimed is:

l. A circuit arrangement comprising a plurality of groups ofmechanically static electric energy translators. such as thermionicvalves of which each comprises a grid, a cathode and an anode, means forapplying a potential to the grid of one of said valves,

-said potential depending on the anode current of another valve inthearrangement.

2. A circuit arrangement comprising a plurality of valves forming aclosed group in which each valve has its grid bias controlled by anothertube of the group, each tube in turn performing a function of grid biascontroller.

3. A circuit comprising a plurality of groups of valves arranged ingroups, one valve being subjected to an impressed pulse adapted tochange its condition as from being operative or non-operative, andresistance elements associated with the said valve which due to saidchange produces an opposite chan e in another valve of the same groupwhic for a predetermined time nfaintains In such a the changed conditionof the first said valve.

4. Circuit as defined in claim 3 characterized in that at least oneresistance element is provided in the output circuit of said valvewhereby input current is supplied to the other of said valves by virtueof the potential drop in said resistance.

r 5. A circuit arrangement comprising thermionic valves in which a valveis adapted to operate as an amplifier only when another valve in thearrangement is paralyzed and when voltage. of'a synchronizing waveapplied to the grid of said first mentioned valve lies within certainlimits.

6. A circuit arrangement according to claim 5 comprising means wherebythe grid -voltage of the first mentioned valve causes the reversal ofvalve conditions therein and the generatiton of a further pulse and soon in sequence.

8. An arrangement according toclaim 1 in which at least one valve of agroup is adapted to be used as a normal amplifier during the time inwhich it is not paralyzed.

9. A high speed telegraph distributor comprising a plurality of spacedischarge tubes connected in pairs and having input and output circuits,resistance elements in said circuits, said elements being so dimensionedthat the input voltage of the second of said devices is the mean of thepotentials at two points of which one point is located in the outputcircuit of the second space discharge device and the other point islocated at the junction point of said input circuit with the point ofapplication of asquare wave which has a voltage smaller than thefilament voltage of said discharge devices.

10. A thermionic repeater comprising at circuit of the first mentioneddevice for correcting the length of the signal impulses transmitted tosaid line.

11. A distributor comprising a plurality of valves interconnectedthrough a plurality of resistance elements for biasing the grids of saidvalves whereby said valves in turn open and close a path for signalcurrents, and means for providing impulses which may be used to operatean external apparatus.

12. A distributor adapted to transmit or receive electric signalimpulses to or from a transmission medium, said distributor comprisingmeans including a space discharge device which when said impulses wouldunduly over-lap in time corrects the length of the impulses, said meansbeing operative only during the length of time desired for the 0impulses.

' 13. A distributor according to claim '12 CARLTON ROSSLYN DUNHAM.

